자료유형  

 학위논문

Control Number  

0017160626

International Standard Book Number  

9798382781594

Dewey Decimal Classification Number  

616

Main Entry-Personal Name  

Qian, Lechen.

Publication, Distribution, etc. (Imprint  

[S.l.] : Harvard University., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

108 p.

General Note  

Source: Dissertations Abstracts International, Volume: 85-12, Section: B.

General Note  

Advisor: Uchida, Naoshige;Murthy, Venkatesh.

Dissertation Note  

Thesis (Ph.D.)--Harvard University, 2024.

Summary, Etc.  

요약Studies on animal learning have shown that the efficacy of both associative learning and responding depends on contingency, the extent to which the likelihood of an outcome changes by a presentation of a stimulus. However, how neural representations in the mesolimbic dopamine system and ventral striatum are modulated by contingency remain unclear. Chapter I of my dissertation focuses on this by examining mice trained in a Pavlovian conditioning degradation task. I observed that anticipatory licking for odors previously associated with rewards significantly diminished when unpredicted rewards were introduced but remained stable with predicted additional rewards. Furthermore, dopamine (DA) axonal signals in the Olfactory Tubercle (OT) and Nucleus Accumbens (NAc), measured using photometry, mirrored these behavioral changes. While dopamine signals are commonly thought to resemble the temporal difference (TD) error in TD learning models, previous studies suggested these models couldn't explain the contingency degradation phenomenon. However, our findings indicated that DA responses in various experimental conditions align closely with a TD learning model incorporating state transitions reflective of task structure. Furthermore, we showed that recurrent neural networks (RNNs) trained in the task using a TD learning framework recapitulate dopamine responses and develop state representations consistent with the task states, merely from observations. Based on these results, we provided a theoretical framework linking TD errors to contingency and causal learning.Many studies of reinforcement learning in rodents have involved the olfactory system. Previous studies have indicated that neural activity related to the odor valence have been observed in the OT, a relatively understudied structure situated in both the olfactory pathway and the ventral striatum. In Chapter II, I examined how valence representations of odor cues evolve over time in the two distinct neuronal populations in the OT, and how stable these representations are under different conditions in contingency learning using 2-photon microscopy. As the idea of representational stability and drift are vigorously debated, this study will add valuable biological data to inform conceptual ideas of neural representations in the brain.Together, these results provided new insights into the neural circuits involved in the representation of contingency in the mammalian brain.

Subject Added Entry-Topical Term  

Neurosciences.

Subject Added Entry-Topical Term  

Cellular biology.

Subject Added Entry-Topical Term  

Molecular biology.

Index Term-Uncontrolled  

Contingency

Index Term-Uncontrolled  

Dopamine

Index Term-Uncontrolled  

Ventral striatum

Index Term-Uncontrolled  

TD-learning

Index Term-Uncontrolled  

Temporal difference

Added Entry-Corporate Name  

Harvard University Biology Molecular and Cellular

Host Item Entry  

Dissertations Abstracts International. 85-12B.

Electronic Location and Access  

로그인을 한후 보실 수 있는 자료입니다.

Control Number  

joongbu:658583